Many people contend with orthopedic issues as a result of age, disease, and trauma, as well as congenital and acquired complications and conditions. While some of these issues can be alleviated without surgery, other issues respond better to surgery. In some cases, surgery may include the insertion of an orthopedic implant. Orthopedic spine assemblies and constructs such as spine plates, bone screw assemblies for spinal rods and other devices (spinal components) have made a profound contribution to the correction of spinal deformities, accidents and other problems in the cervical as well as thoracic, lumbar and sacral spine. These and other spinal devices are typically fixed to vertebrae using vertebral bone screws. Vertebral bone screws are specially designed and manufactured bone screws that are placed into the bone of a vertebra. Vertebral bone screws placed in the vertebra offer superior strength and pull-out resistance as compared to other forms of fixation in spine surgery. The ability to achieve vertebral fixation has allowed surgeons to obtain more secure fixation of the spinal components involved, which permits more powerful correction of spine problems and reported better clinical outcomes.
In addition to other uses, bone screws provide a solid foundation for the attachment of spinal rods. Spine rods are used for the fixation of a plurality of vertebrae for various situations. A spine rod is held relative to the vertebrae by a spine rod bone screw assembly. Various types of spine rod bone screw assemblies are known such as those that allow for inter-operative adjustments in the coronal, transverse and sagittal planes—generally known as poly-axial spine rod bone screw assemblies. Certain spine rod bone screw assemblies allow for various degrees of freedom of attachment of a spine rod thereto from any direction, angle, and height. In all cases, however, the spine rod bone screw assemblies hold a spine rod and are fixed to a vertebra. The poly-axial spine rod bone screw assembly thus permits spine rods to be rigidly locked into a variety of positions along with other types of implant components. This allows a surgeon to tailor-make each construct.
One type of poly-axial spine rod bone screw assembly is known as a poly-axial tulip head spine rod holder. The poly-axial tulip head spine rod holder consists of a poly-axial bone screw, a poly-axial head that is shaped like a tulip (poly-axial tulip head), and an insert within the poly-axial tulip head. The poly-axial tulip head is situated about the poly-axial bone screw head while the insert is situated within the poly-axial tulip head, the insert that interacts with the bone screw head and the tulip head. Downward pressure exerted against the insert during installation of a spine rod and set screw in the poly-axial tulip head causes the insert to bind against the poly-axial bone screw head and between the poly-axial tulip head such that the orientation of the tulip head is fixed relative to the bone screw. While current poly-axial tulip head spine rod holders are adequate, there is room for improvement.
Thus, there is a need for an improved poly-axial tulip head spine rod bone screw assembly.